Creep Curve Modeling of Hastelloy-X Alloy by Using the Nonlinear Regression Method in the Kachanov-Rabotnov Creep Model

Abstract

To design HTGR components for up to 1000oC, their creep curves are necessary during a
design process. In this study, the full creep curves were modeled by the nonlinear least square fitting
method using the Kachanov-Rabotnov (K-R) creep model. A series of creep data was obtained
experimentally under various stress levels for Hastelloy-X at 950oC, and the data was used to model
the creep curves. The K-R model gave a poor description of modeling creep curves, but the modified
K-R one, which has another variable, K in the K-R model, was in better agreement than the K-R one. It
was found that the λ parameter in the K-R model was constant regardless of the stress variations. The
λ value was about 3.9 for the K-R model and about 5.8 for the modified one.